Put a copy of the Empty String/Path? on the Variant palette since "this function is also designed to work with variants...; see https://www.ni.com/docs/en-US/bundle/labview/page/glang/empty_string_path.html .
For an example of the difficulty in finding this function, see https://forums.ni.com/t5/forums/editpage/board-id/170/message-id/1248895
For precedent of the same functions on different palettes see the Array to Cluster and Cluster to Array functions on both the array and the cluster palettes.
